IPv6: TLLA must be included with NA sent to multicast address

[Mike Belopuhov]

RFC 4861 says:

      Target link-layer address
                     The link-layer address for the target, i.e., the
                     sender of the advertisement.  This option MUST be
                     included on link layers that have addresses when
                     responding to multicast solicitations.  When
                     responding to a unicast Neighbor Solicitation this
                     option SHOULD be included.

                     The option MUST be included for multicast
                     solicitations in order to avoid infinite Neighbor
                     Solicitation "recursion" when the peer node does
                     not have a cache entry to return a Neighbor
                     Advertisements message.

diff --git sys/netinet6/nd6_nbr.c sys/netinet6/nd6_nbr.c
index 90e7d19..c6cd139 100644
--- sys/netinet6/nd6_nbr.c
+++ sys/netinet6/nd6_nbr.c
@@ -605,6 +605,13 @@ nd6_na_input(struct mbuf *m, int off, int icmp6len)
                goto freeit;
        }
 
+       if (IN6_IS_ADDR_MULTICAST(&daddr6) && !ndopts.nd_opts_tgt_lladdr) {
+               nd6log((LOG_INFO,
+                   "nd6_na_input: multicast adv without TLLA\n"));
+               /* nd6_options have incremented stats */
+               goto freeit;
+       }
+
        if (ndopts.nd_opts_tgt_lladdr) {
                lladdr = (char *)(ndopts.nd_opts_tgt_lladdr + 1);
                lladdrlen = ndopts.nd_opts_tgt_lladdr->nd_opt_len << 3;